In fluid operated systems, both pneumatic and hydraulic, various pressure levels may be required throughout the system. To provide those various pressure levels, a high line pressure is reduced by use of pressure reducing valves wherever lower supply pressure levels are required. These pressure reducing valves add to the cost of the system, to the installation complexity and to maintenance costs. Pressure reducing valves also add restrictions to the system flow, even when fully open, and thus increase the energy requirements of the system. Further, in order to compensate for the reduced flow through the restrictions of the open reducing valves, larger main supply valves in the control valves are required. Thus, the cost of the system is increased not only by the cost of the pressure reducing valves themselves but also by the cost of providing larger supply valves.
A primary application of pressure reducing valves is in limiting the pressure applied during the return stroke of a piston after it is driven by full line pressure. In conventional systems, supply pressure is applied to and vented from each end of a cylinder by a four-way supply and waste control valve. In a four-way valve, the fluid is supplied to a first load conduit as it is exhausted from a second conduit, and thereafter the fluid is exhausted from the first conduit and supplied to the second conduit. Thus, as high pressure fluid is supplied through a first load conduit to a first end of the cylinder, it is exhausted from the second end of the cylinder through the second load conduit. Thereafter, the high pressure fluid is supplied to the second end of the cylinder through the second load conduit and is exhausted from the first end of the cylinder through the first load conduit. Where less than full line pressure is required to drive the piston in either or both directions, one or more pressure reducing valves can be positioned in the load conduits between the four-way supply and waste control valve and the cylinder.